28. At this time, the general weather conditions of M and N are () A, M and N are sunny, B, M and N are rainy, and C, M, D and N are rainy.

In the picture, a front is formed on the trough of low pressure, and the warm air mass actively moves closer to the cold air mass, forming a warm front. In the horizontal direction of the cyclone in the northern hemisphere, the airflow flows counterclockwise from the periphery to the center, m is located behind the warm front, controlled by a single warm air mass, and the weather is fine; N is located in front of the warm front, with precipitation weather.

Therefore, choose: d.